Industries in general, and the power industry in particular, place a high emphasis on the reliability of valve operators and other electrically actuated devices. The correct operation of these electrically actuated devices have direct effects on the improvement or maintenance of plant output, and furthermore provide for the protection of other plant equipment. Often, the valves or other devices are required to operate under varying operating conditions of temperature, pressure, and flow of materials therethrough. Furthermore, the inherent operating characteristics of the electrically actuated devices and device actuators are continuously undergoing mechanical or electrical changes from maintenance, repair, adjustments, calibration and wear. Therefore, there is a great need for systems which can monitor the use, operability and reliability of such electrically actuated devices.
In particular, the valves and operators used in nuclear power plants often serve as an important component in the overall system to protect against the release of radioactive materials. Due to the vast number of valves and operators utilized in a typical nuclear power plant, the nuclear industry is fully aware of the importance of maintaining proper and continuous operation of these valves and operators as well as the need for ascertaining the probable life expectancy of the electrically actuated devices utilized therein.
Prior art systems have been proposed for the evaluation of valve and valve operator systems, particularly systems which are motor or otherwise power driven and are operated from a remote location. One proposed system for monitoring and maintaining proper operation of these critical valves is disclosed in U.S. Pat. No. 4,542,649, issued to Charbonneau et al. The system disclosed therein is directed to a valve operator and monitoring system which measures, records and correlates valve stem load, limit and torque switch positions, spring pack movement and motor current providing time related information on valve performance. The information produced by the system of this prior patent purports to provide a direct indication of developing valve and valve operator problems. Such problems include excessive or inadequate packing load, excessive inertia, proximity to premature tripping, incorrect settings of operating limit and torque switches, improperly functioning thermal overload devices, inadequate or excessive stem thrust loads, gear train wear, stem damage, and load relaxation. The Charbonneau et al patent states that this system provides for the measurement of current flowing through the operator limit and torque switches in order to provide other diagnostic data.
One of the major drawbacks of this and conventional prior art systems directed to the monitoring of the operation cycles of valves or other current actuated devices is that there is no provision for on-line cyclic counting of the total number of valve actuations. The useful life of a device can often be accurately estimated in terms of the number of actuations the device has undergone. By counting the number of actual activations, one can accurately estimate the remaining useful life of the device.
Previously proposed systems provide for off-line testing and involve the utilization of complex configurations of numerous instruments and recording equipment. For example, monitoring systems for instance, rely on computer monitoring and data recording by strip chart recorders in order to accumulate the diagnostic data of equipment when it is removed from its working environment. In such systems lengthy analysis of the diagnostic data, including the comparison of past and present strip charts generated by a series of bench tests of the equipment are not deemed to be an efficient diagnostic tool. In addition, various regulations may prohibit intrusions into the actuating system during actual operation without following substantial and burdensome procedures.
It is therefore an object of the present invention to provide a device which monitors electrical parameters of an electrically actuated device.
It is a further object of the present invention to provide a monitoring system which is capable of counting the operation cycles of a valve or other electrically actuated device to help estimate the remaining useful life of the device.
It is another object of the present invention to provide non-intrusive measurement of the operation cycles of the electrically actuated device, and thus achieve on-line cycle counting of these operations. This type of measurement obviates the need for shutting down the electrically actuated devices that is required for bench testing.
It is a further object of the present invention to provide an actuation counter which displays real-time output of operation cycles of the device being monitored.
It is still a further object of the present invention to provide an actuation counter in a small portable housing to promote easy installation in areas not readily accessible by large instruments.
An additional object of the present invention is to provide an accurate count of the total number device actuations as a measure of age and remaining useful life, thereby providing an indication of the device's reliability.
It is a further object of the present invention to provide a system which contributes to the process control of a monitored device by providing a count relating to, for example, the number of products on a specified production line or the number of on/off cycles of components such as heaters which are associated with the monitored device.
Furthermore, it is another object of the present invention to provide a system which is capable of monitoring current fluctuations of a current supplied to an electrically actuated device. An accurate measurement of current fluctuation is an aid in determining the existence of problems in the monitored device and estimating the remaining useful life of the monitored device
These and other objects are achieved by the actuation counter according to the present invention which counts the number of operational cycles of an electrically actuated device. The actuation counter has associated therewith a probe which detects the presence of an electrical parameter on a conductor which carries current to the electrically actuated device. The probe generates a signal corresponding to each detection of the electrical parameter. The electrical parameter, which can be current or voltage, is generated on the conductor in order to actuate an operational cycle of the electrically actuated device. A counter circuit is provided and is operable for incrementing a stored count to a present count in response to receiving the signal from the probe which signal corresponds to the detection of the electrical parameter. A display is coupled to the counter circuit for displaying the present count of the counter circuit.
In another aspect of the present invention, the probe is operable for inducing a first voltage after detecting the presence of the actuation electrical parameter. A threshold setting circuit is coupled to the probe for setting a threshold value of the actuation electrical parameter at which the probe induces the first voltage. An amplifier is preferably coupled to the threshold setting circuit in order to amplify the first voltage to produce a second voltage. The counter circuit increments the stored count therein to a present count in response to an increment input of the counter circuit being supplied with a low voltage. The increment input of the counter circuit is otherwise maintained at a high voltage. A voltage reducing circuit, which is coupled between the amplifier and the increment input, receives the second voltage and thereafter drives the increment input with a low voltage to increment the present count. The display continuously displays the present count which corresponds to a real-time count of the operation cycles of the electrically actuated device.
According to another aspect of the present invention, a portable monitoring system obtains a count of a number of operation cycles of a current actuated device. The monitoring system produces a real-time output of the count. In addition to the features noted above, the counting circuit is arranged in a portable housing. The counting circuit also includes an operational amplifier which receives the voltage induced by the probe and transforms the voltage into an increment voltage. A counter stores and increments the count in response to an increment input of the counter supplied with a low voltage. Otherwise the increment input is supplied with a relatively high voltage of an associated battery. A transistor has its base terminal coupled to receive the increment voltage from the operational amplifier and its collector terminal connected to the increment input such that, upon the base terminal receiving the increment voltage, the collector terminal drives the increment input with a low voltage. This low voltage initiates a count increment by the counter.
In accordance with a further aspect of the present invention, a set of external access ports is provided to permit generation of an external reading of the increment voltage. A reset switch is provided to reset the counter to a count of zero. Further, a display for the count provides a real-time output of the number of operation cycles of the current actuated device.